The plastics industry is one of the largest consumers of organic and inorganic fillers. The total consumption of different types of fillers was about 3.5 million MT in the year 1983 and it is increasing at a rate of 4 to 5% annually. Inorganic fillers such as calcium carbonate, talc, mica and the like are well known, as well as organic fillers such as wood flour, chaff and the like, fibrous materials such as asbestos and glass fiber, as well as graphite, cokes, blown asphalt, activated carbon, magnesium hydroxide, aluminum hydroxide and the like. All of these additives have high specific gravities and their ability to improve physical properties of the composition is limited.
Flax is a commercially important plant fiber crop being grown either for its seed (used in the production of linseed oil) or for its fiber or both. The major industrial uses of flax fiber are in textiles (in the manufacture of linen household textile, linen furnishing fabrics, linen clothing, etc.) and the manufacture of pulp and paper. In the pulp and paper industry, flax fibers are currently used in the production of thin strong papers such as cigarette papers, airmail papers, currency papers, high quality permanent record bond papers and high quality writing papers.
Another possible use for flax fiber is in the filling and reinforcement of thermoplastic matrix resins, such as polyethylene and polypropylene. Composites of these plastics with lignocellulosic fillers (e.g. wood flour) are already in commercial use, for example, in such applications as interior molded auto parts (e.g. dash and door panels, trunk liners), exterior plastic-composite lumber and furniture components.
The potential of using flax fibers in plastic applications as a substitute for synthetic fibers such as glass, carbon, nylon, polyester, etc. has been recognized. For example, GB 2090849 describes the incorporation of flax bast fibers into a thermoplastic resin blend. The use of flax bast fibers for reinforcing resins results in processing problems, as the flax bast fibers tend to "ball up" during processing. Thermosetting resin blends containing flax shives or combinations of shives and less than about 30 weight percent bast fibers are not described. Further, purposeful attempts have been made to exclude flax shive from flax fiber preparations used for reinforcing composites. For example, Mieck et al. (Polymer Composites, December 1996, Vol. 17, No. 6), suggest that for better composite characteristics, the fibers should be free from shives.
An object of the present invention is to provide a resin composition that is reinforced with flax shives.
It is another object of the invention to provide a method for reinforcing thermosetting resin compositions.
Other objects, advantages, features and characteristics of the present invention will become more apparent upon consideration of the following description and the appended claims.